Dr. Mahmud Abuauba MBChB, DCH, MD, PhD Consultant Pediatrician & pediatric Nephrologist Assistant Professor of Pediatrician

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1 RENAL BLOOD SUPPLY & FLOW Dr. Mahmud Abuauba MBChB, DCH, MD, PhD Consultant Pediatrician & pediatric Nephrologist Assistant Professor of Pediatrician Zawia Kidney Center 5 th May 2018

2 برعاية مركز عالج أمراض الكلى-الزاوية

3 RENAL BLOOD SUPPLY

4 RENAL BLOOD SUPPLY Both kidneys receive approx. 21% (20 25%) of cardiac output, at rest 1200 ml/min ( ml/min) = High blood supply ~ 4 ml/g/min of kidney tissue; why? Not only, to supply oxygen & nutrients, etc. To control precisely fluid, electrolytes & acid-base balance To remove waste products rapidly

5 RENAL BLOOD SUPPLY Renal oxygen comsumption is high ~6 ml/100g/min, which correlates with Na-K pump & renal blood flow Entire blood circulates through the glomeruli every 4-5 min

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9 RENAL ARTERY Each kidney receives a single main renal artery (Rt &Lt) From abd. Aorta at Rt angle, at L 2 Lt RA is shorter In about 30%, accessory RA or abberent RA, no veins, lower pole Main RA gives branches to adrenal gland, renal pelvis, ureter, renal capsule & perirenal fat

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12 Left renal vein is longer than the right renal vein

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14 Division arteries Each main RA upon or just arrival to hilum divides into two divisions or branches: Anterior branch to anterior part of kidney Posterior branch to posterior part of kidney Supplying five vascular segments

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16 Segmental arteries Pos. division supplies only pos. segment Ant. division to four segments; apical, upper, middle & flower While still in hilum, these 2 branches give rise to 5 segmental arteries (5) with each one supplies one segment No anastomoses be segmental As Have surgical importance, end As

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21 LOBAR ARTERY Initial branch of Seg. A is lobar As before entry into renal substance One for each renal pyramid or renal lobe Just before entry into renal substance, gives 2-3 interlobar As That run between renal pyramids towards the cortex

22 ARCUATE ARTERY I At corticomedullary border, interlobar artery divides into arcuate arteries at right angle Interlobular As arise from arcaute arteries at right angle Interlobular arteries form borders of renal lobule

23 ARCUATE ARTERY II Ascend toward the renal capsule, end as capsular plexus No anastomoses between arcaute As, Arcuate arteries are considered as end arteries Arcuate A ends as interlobular A

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26 Afferent glomerular arteriole Interlobular As run in center of cortical labyrinth They form the borders of renal lobules Each gives rise to many AGAs AGAs are short, stright, enter renal corpuscle at vascular pole Each AGA divides into a tuft of capillaries forming glomerulus

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28 Renal Corpusle

29 GLOMERULUS Each afferent glomerular arteriole divides into 3-5 branches then a tuft of capillaries (20-40 loops) Forms the glomerulus Capillaries coalesce again to form efferent glomerular arteriole EGA is longer & narrower, why AGA is shorter, striaght & wider

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31 PERITUBULAR CAPILLARIES EGA of cortical nephrons breaks into another set of capillaries called peritubular capillary plexus Surrounds PCT, DCT & CCT Supplies entire cortical labyrinth, except glomerulus Epo, 90% in peritubular capillary endothelial cells, 10% in the liver

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33 Vasa recta I EGA of juxtamedullary nephrons breaks into another set of thin & long capillaries called vasa recta Accompanies Henel s loop Vasa recta formed of: arteriole recta descending branches vena recta, ascending branches

34 Vasa recta II Arteriole recta has nonfenestrated endothelial cells, single layer Vena recta has fenestrated endothelial cells Supply blood to medulla (1-3%), for nutrients & O2 Form basis of CCE & CCM All endothelial cells of nephrons are fenestrated, except descending vasa recta

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37 VENOUS RETURN Venous end of PTCP convey to form interlobular veins Capillaries of outer cortex & renal capsule converge to form stellate veins which empty into interlobular veins Then follows arterial system

38 VENOUS RETURN There are anastomoses There are no segmental or lobar V Unite at hilum, renal vein, Rt & Lt IVC to heart

39 RENAL BLOOD SUPPLY Has two capillary sets Glomerulus & PTCP seperated by EGA This arrangement helps to regulate glomerular filtration Glomerular hydrostatic pressure is 60 mm Hg & PTCP is 13 mm Hg glomerular filtration & tubular reabsorption

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41 RENAL BLOOD SUPPLY Surface area of renal capillary = SA of tubules= 12 m 2 Total SA for filtration = 0.8 m 2 Volume of blood in capillaries is ml

42 NORMAL CIRCULATION Heart Veins Arteries Venules Arterioles Capillaries

43 RENAL CIRCULATION Veins Heart arteries Arterioles Venules glomerulus PTC arterioles

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47 RENAL BLOOD FLOW

48 RENAL BLOOD FLOW

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52 Renal Blood Flow Effective renal plasma flow (ERPF)= CPAH = UPAH X V = 585 ml /min PPAH TRPF = / extraction ratio = 585/ CPAH 0.9= 650 ml/min TRBF = TRPF = 1200 ml/min 1 - HCT

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56 AUTOREGULATION A mechanism by which RBF & GFR remain constant despite change in RABP ( mmhg), WHY? If GFR is 125ml/min so 180L/day is formed where 178.5L/day reabsorbed & 1.5L/day is urine, at BP ~100mmHg If BP rises from 100 to 125 mm Hg so GFR rises from 180 to 225L/day, 178.5L/day reabsorbed & 46.5L/day is lost, fatal

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65 THANKS FOR ATTENTION